Mentor: Arijit Bose, University of Rhode Island
Co-Mentor: Irene Andreu, University of Rhode Island

Project Location

University of Rhode Island-Kingston

Project Description

This project involves the development of a new type of liquid cell for in situ transmission electron microscopy (TEM). Many physical, chemical and biological phenomena taking place in liquids would benefit from imaging at the nanoscale. This is typically done using transmission electron microscopy (TEM). But the high vacuum required in TEM is incompatible with having liquid samples, as the liquid will evaporate rapidly. This makes it impossible to obtain images of nanoscale materials in their native states. A group at UC Berkeley has developed a new technique that overcomes this difficulty. The technique is based on entrapment of a liquid film of the sample between layers of graphene. van der Waals forces at the edges of the graphene sheets seal the sample. Because graphene is electron transparent, the electron beam is not attenuated as it enters or leaves the sample. The new transmission electron microscope at URI is also equipped with a direct electron camera, allowing rapid imaging and thus the potential to observe transient evolution of structures at the nanoscale. The graphene liquid cell facilitates atomic-level resolution imaging while sustaining the most realistic liquid conditions achievable under electron-beam radiation.

The technique: A graphene sheet is placed on a TEM grid. The liquid sample is then placed on this sheet, and a second graphene sheet is used to close the cell. van der Waals forces hold the two sheets together, and the sample is sandwiched in between.

The SURF student involved in this project will help develop graphene liquid cell capability. As a model test system, we will first look at the hydration of calcium sulfate hemihydrate (CaSO4· 0.5H2O) to form gypsum (CaSO4·2H2O). We will trigger crystallization by perturbing a supersaturated solution of the calcium hemihydrate using the electron beam. We will monitor, in situ, crystal growth dynamics and phase transitions from a supersaturated solution. We will introduce additives, designed to suppress the amorphous to crystalline phase transition. By combining this GLC with the direct electron camera we expect to be able to monitor changes in morphology as well as phase in second to sub-second time scales. This data will be novel and transformative.

Once we have demonstrated in situ nanoscale imaging in liquids, we plan to offer this capability to the wider URI community for looking at a range of chemical, biological and physical samples.